Percentage calculations at a summary level

As a services company our key measurement is resource utilization. We report by person and summarize by department also. The calculation we use is billable hours / (scheduled hours - time off hours). At a summary level Replicon takes an average of all of the resources in the department instead of calculating at the summary level the sum of billable hours / (scheduled hours - time off hours) for the department. The calculations are not the same and are incorrect at the summary level.